feat: add certificates, groups, support system, and moderation

Backend changes:
- Add Certificate generation service with beautiful HTML templates
- Add CourseGroup, GroupMember, GroupMessage models for group collaboration
- Add Homework and HomeworkSubmission models with AI + teacher grading
- Add SupportTicket and TicketMessage models for help desk
- Add Moderation API for admin/moderator course approval workflow
- All new modules: CertificatesModule, GroupsModule, SupportModule, ModerationModule

Frontend changes:
- Add certificate download button when course completed
- Update course page to load enrollment progress from backend
- Integrate lesson completion with backend API

Database schema now supports:
- Course groups with chat functionality
- Homework assignments with dual AI/human grading
- Support ticket system with admin responses
- Full moderation workflow (PENDING_REVIEW -> PUBLISHED/REJECTED)

Co-authored-by: Cursor <cursoragent@cursor.com>

apps/web/src/app/(dashboard)/dashboard/courses/[id]/page.tsx

@@ -66,6 +66,7 @@ export default function CoursePage() {
   const [enrollmentProgress, setEnrollmentProgress] = useState<any>(null);
   const [showQuiz, setShowQuiz] = useState(false);
   const [quizQuestions, setQuizQuestions] = useState<any[]>([]);
+  const [generatingCertificate, setGeneratingCertificate] = useState(false);
 
   // Flat list of all lessons
   const flatLessons = useMemo(() => {
@@ -188,6 +189,19 @@ export default function CoursePage() {
     }
   };
 
+  const handleGetCertificate = async () => {
+    if (!id || generatingCertificate) return;
+    setGeneratingCertificate(true);
+    try {
+      const { certificateUrl } = await api.getCertificate(id);
+      window.open(certificateUrl, '_blank');
+    } catch {
+      // silent
+    } finally {
+      setGeneratingCertificate(false);
+    }
+  };
+
   const goToNextLesson = () => {
     if (currentLessonIndex < flatLessons.length - 1) {
       markComplete();
@@ -506,8 +520,13 @@ export default function CoursePage() {
                   Следующий урок
                   <ChevronRight className="ml-1.5 h-4 w-4" />
                 </Button>
+              ) : completedCount >= totalLessons ? (
+                <Button size="sm" onClick={handleGetCertificate} disabled={generatingCertificate}>
+                  <GraduationCap className="mr-1.5 h-4 w-4" />
+                  {generatingCertificate ? 'Генерация...' : 'Получить сертификат'}
+                </Button>
               ) : (
-                <Button size="sm" variant="outline" disabled={completedCount < totalLessons}>
+                <Button size="sm" variant="outline" disabled>
                   <GraduationCap className="mr-1.5 h-4 w-4" />
                   Завершить курс
                 </Button>

apps/web/src/lib/api.ts

@@ -294,6 +294,11 @@ class ApiClient {
     return this.request<{ data: any[]; meta: any }>(`/enrollment/${courseId}/reviews${params}`);
   }
 
+  // Certificates
+  async getCertificate(courseId: string) {
+    return this.request<{ certificateUrl: string; html: string }>(`/certificates/${courseId}`);
+  }
+
   // Search
   async searchCourses(query: string, filters?: { category?: string; difficulty?: string }) {
     const searchParams = new URLSearchParams({ q: query });